It might be attacked slowly by air oxygen and not accumulate peroxides as a result. It may also be hydrolysed by air humidity as well. The likely uses of this solvent may be performance sensitive to purity and the manufacturer gives a conservative enough warning so that users won't be disappointed.Even in the case of low level, not unsafe, peroxide presence in solvents like ether, some uses can be sensitive to peroxide presence.Another organic liquid, tetramethylethylenediamine (TEMED), used in acrylamide gel formation, will auto-oxidize to a fairly advanced, but not hazardous extent (no real peroxide accumulation), giving a yellow or orange color, which will sabotage the gel formation. The hazard there is mostly in the reaction of the user to this result.

During a lab inspection today, I noticed a bottle of extra pure Dimethylformamide in one of our labs that had a note on the manufacturers (Acros) label that says "use within 5 years of opening". A little Google searching doesn't seem to indicate the DMF is a peroxide former, so I wonder if anyone can shed some light on why this time limit is recommended?

The bottle was received in Jan 2011, so inquiring miles would like to know.

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